1. Field of the Invention
The present invention relates to a process for assembling a belt for a continuously variable transmission by assembling a large number of metal elements along a metal ring assembly comprised of a plurality of endless metal rings laminated one on another.
2. Description of the Related Art
The belt for the continuously variable transmission is constructed by assembling a large number of metal elements along a metal ring assembly. However, each of the metal elements is produced by finely blanking a metal plate and for this reason, a dimensional variation is unavoidably generated in thickness of the metal element for every lot, and a dimensional variation is also unavoidably generated in peripheral length of the metal ring assembly. Therefore, the following problem is encountered: When a predetermined number of the metal elements are assembled to the metal ring assembly, the variations in thickness of the large number of metal elements are accumulated, whereby the metal ring assembly becomes relatively too long and a large clearance incapable of being disregarded for the durability of the belt for the continuously variable transmission is generated between the metal elements after completion of the assembling; or the metal ring assembly becomes relatively too short, only a number of the metal element one smaller than the predetermined number is assembled and as a result, a large clearance incapable of being disregarded is generated between the metal elements.
Therefore, Japanese Utility Model Application Laid-open No. 61-103651 discloses a technique in which standard elements having a standard thickness are combined among a predetermined number of adjusting elements having a thickness slightly larger than that of the standard elements, thereby decreasing the clearance between the elements.
To assemble the belt for the continuously variable transmission by combining the adjusting elements among the standard elements, the standard elements as many as possible are first assembled to the metal ring assembly; an initial clearance defined between the rearwardmost and forwardmost ones of the standard elements is measured, and the number of the adjusting elements required is determined in accordance with the initial clearance. To assemble the number of the adjusting elements required, a predetermined number of the standard elements already assembled are removed from the metal ring assembly, and in place of them, the adjusting elements are assembled.
From the forgoing, there is encountered a problem; if the number of the adjusting elements required is increased, the number of the standard elements removed after being once assembled to the metal ring assembly is also increased, resulting in an increased number of operating steps. In addition, since the standard elements and the adjusting elements are different in thickness from each other and, for example, a dimensional variation unavoidably exists between heights of saddle faces with which the metal ring contacts, there is a possibility that the durability of the belt for the continuously variable transmission is adversely affected by a load applied to the metal ring assembly by the metal element whose saddle faces protrude. Therefore, it is desirable to minimize the number of the adjusting elements to be combined among the standard elements.
FIG. 6 is a graph showing how many adjusting elements having a thickness of 1.6 mm are required for compensating for the initial clearance xcex1i generated when standard elements having a standard thickness t of 1.5 mm are used. In this case, xcex94t which is a difference between the standard thickness t=1.5 mm of the standard elements and the thickness 1.6 mm of the adjusting elements, is 0.1 mm.
The case where the initial clearance xcex1i is equal to 0.0 mm is an ideal state in which only the standard elements are used without using the adjusting elements, resulting in no clearance xcex1 generated between the elements. If 0.0 mm less than xcex1i less than 0.1 mm, it is impossible to compensate for the initial clearance xcex1i by the adjusting elements, and only the standard elements are used. However, the clearance xcex1 between the elements is such small as 0.1 mm or less, and there is no particular hindrance in practical use. From the forgoing, if 0.0 mmxe2x89xa6xcex1i less than 0.1 mm, the number of the adjusting elements required is 0 (zero).
If 0.1 mmxe2x89xa6xcex1i less than 0.2 mm, the clearance xcex1 between the elements can be suppressed to 0.0 mm or more and less than 0.1 mm by using one adjusting element, and if 0.2 mmxe2x89xa6xcex1i less than 0.3 mm, the clearance xcex1 between the elements can be suppressed to 0.0 mm or more and less than 0.1 mm by using two adjusting elements. Likewise, whenever the initial clearance xcex1i is increased by 0.1 mm, the number of the adjusting elements required is increased one by one, and finally, if 1.4 mmxe2x89xa6xcex1i less than 1.5 mm, the clearance xcex1 between the elements can be suppressed to 0.0 mm or more and less than 0.1 mm by using fourteen adjusting elements. Therefore, it is understood that when only the adjusting elements having a thickness of 1.6 mm are used, average seven adjusting elements are required to suppress the clearance xcex1 between the elements to less than 0.1 mm.
FIG. 7 is a graph showing how many adjusting elements having a thickness of 1.4 mm are required to compensate for the initial clearance xcex1i generated when standard elements having a standard thickness t of 1.5 mm are used. In this case, xcex94t which is a difference between the standard thickness t=1.5 mm of the standard elements and the thickness 1.4 mm of the adjusting elements, is 0.1 mm.
The case where the initial clearance xcex1i is equal to 1.5 mm in an ideal state in which only the standard elements are used without using the adjusting elements, resulting in no clearance xcex1 generated between the elements. If 1.4 mm less than xcex1i less than 1.5 mm, the clearance xcex1 between the elements can be suppressed to 0.0 mm or more and less than 0.1 mm by using one adjusting element, and if 1.3 mmxe2x89xa6xcex1i less than 1.4 mm, the clearance xcex1 between the elements can be suppressed to 0.0 mm or more and less than 0.1 mm by using two adjusting elements. Likewise, whenever the initial clearance xcex1i is decreased by 0.1 mm, the number of the adjusting elements required is increased one by one, and finally, if 0.0 mmxe2x89xa6xcex1i less than 0.1 mm, the clearance xcex1 between the elements can be suppressed to less than 0.1 mm by using fifteen adjusting elements. If xcex1i=0.0 mm, since the clearance xcex1 between the elements can be suppressed to 0.1 mm by using only the standard elements, the second adjusting element 32b is not required. Therefore, it is understood that when only adjusting elements having a thickness of 1.4 mm are used, average eight adjusting elements are required to suppress the clearance xcex1 between the elements to less than 0.1 mm.
The present invention has been accomplished with the above circumstance in view, and it is an object of the present invention to decrease the number of the adjusting elements required for suppressing the clearance between the elements for the belt for the continuously variable transmission to a predetermined value or less.
To achieve the above object, according to a first feature of the present invention, there is provided a process for assembling a belt for a continuously variable transmission by assembling a large number of metal elements along a metal ring assembly comprised of a plurality of endless metal rings laminated one on another. The process comprises the steps of preparing, as the metal elements, standard elements having a standard thickness t, first adjusting elements having a thickness larger than the standard thickness t by a predetermined value xcex94t, and second adjusting elements having a thickness smaller than the standard thickness t by a predetermined value xcex94t; assembling only the standard elements closely on the metal ring assembly, and defining, as an initial clearance xcex1i, a clearance xcex1 generated between the rearwardmost and forwardmost ones of the standard elements, when the number of standard elements assembled has reached the maximum; if the initial clearance xcex1i is smaller than approximately one half of said standard thickness t, combining a predetermined number of said first adjusting elements among said standard elements, thereby making the clearance xcex1 after completion of the assembling to smaller than said predetermined value t; or if the initial clearance xcex1i is equal to or larger than approximately one half of said standard thickness t, combining a predetermined number of said second adjusting elements with said standard elements to assemble them, thereby making the clearance xcex1 after completion of the assembling to smaller than said predetermined value t.
With the above feature, the first adjusting elements thicker than the standard elements having the standard thickness t by the predetermined value xcex94t and the second adjusting elements thinner than the standard elements having the standard thickness t by the predetermined value xcex94t are prepared, a predetermined number of the first adjusting elements or the second adjusting elements are combined among the standard elements, depending on whether the initial clearance xcex1i is smaller than, or equal to or larger than substantially one half of the standard thickness t, thereby suppressing the clearance xcex1 between the elements after completion of the assembling to smaller than the predetermined value xcex94t. Therefore, the number of the adjusting elements required can be reduced to about one half, as compared with a case where only the first adjusting elements or the second adjusting elements are used to achieve the adjustment irrespective of the initial clearance xcex1i.
As a result, it is possible to reduce the number of operating steps for replacing the already assembled standard elements by the adjusting elements after measurement of the initial clearance xcex1i. Moreover, even when a difference in height level exists between saddle faces of the standard element and the adjusting element, a load acting on the metal ring assembly due to the difference in height level can be minimized, to thereby enhance the durability of the belt for the continuously variable transmission.
According to a second feature of the present invention, in addition to the first feature, if xcex94txe2x89xa6xcex1i less than (t+xcex94t)/2, the predetermined number of the first adjusting elements are combined among the standard elements, or if (t+xcex94t)/2xe2x89xa6xcex1i less than t, the predetermined number of the second adjusting elements are combined among the standard elements.
With the above feature, if xcex94txe2x89xa6xcex1i less than (t+xcex94t)/2, the first adjusting elements are used, or if (t+xcex94t)/2xe2x89xa6xcex1i less than t, the second adjusting elements are used. Therefore, it is possible to minimize the number of the second adjusting elements required when the initial clearance xcex1i is approximately one half of the standard thickness t.